Mobile wireless communications device with reduced interfering RF energy into RF metal shield secured on circuit board

ABSTRACT

A mobile wireless communications device includes a housing and circuit board carried by the housing and having RF circuitry comprising at least one RF component and plurality of other components mounted on the circuit board. An RF metal shield is secured to the circuit board and surrounds and isolates the at least one RF component and plurality of other components within the RF metal shield. An RF absorber is positioned adjacent an area of the RF component that radiates energy to aid in reducing energy radiated from the RF component into the RF metal shield.

FIELD OF THE INVENTION

The present invention relates to the field of communications devices,and more particularly, to mobile wireless communications devices andrelated methods.

BACKGROUND OF THE INVENTION

Cellular communication systems continue to grow in popularity and havebecome an integral part of both personal and business communications.Cellular telephones allow users to place and receive phone calls mostanywhere they travel. Moreover, as cellular telephone technology isincreased, so too has the functionality of cellular devices. Forexample, many cellular devices now incorporate Personal DigitalAssistant (PDA) features such as calendars, address books, task lists,calculators, memo and writing programs, etc. These multi-functiondevices usually allow users to wirelessly send and receive electronicmail (email) messages and access the internet via a cellular networkand/or a wireless local area network (WLAN), for example.

As the functionality of cellular communications devices continues toincrease, so too does demand for smaller devices that are easier andmore convenient for users to carry. As any circuit boards and electroniccomponents thereon are reduced in size and placed closer together,including antenna and microphone components, various electroniccomponents can pick up conductive energy and create interference withinthe system.

Many of the designs include an RF metal shield secured onto the printedcircuit board, and surrounding and isolating different RF components,including transceiver chip sets such as multi-chip modules, which aresecured on the circuit board within the housing. The RF metal shieldencloses these components and chip sets. Some of the RE components orchip sets radiate RF energy to other chips or components that are inclose proximity from electromagnetic coupling through the RF metalshield. This type of electromagnetic coupling (EMC) or electromagneticinterference (EMI) coupling causes interference to the RF circuits, anddegrades RF performance, such as receiver sensitivity. Thus, the RFmetal shield that is supposed to shield the components from extraneousRF energy can in and of itself create electromagnetic coupling problemswith different RF components that are supposed to be shielded within theRF shield.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages will become apparent from thedetailed description which follows when considered in light of theaccompanying drawings in which:

FIG. 1 is a schematic block diagram of an example of a mobile wirelesscommunications device configured as a handheld device that can be usedand illustrating basic internal components thereof.

FIG. 2 is a front elevation view of the mobile wireless communicationsdevice of FIG. 1.

FIG. 3 is a schematic block diagram showing basic functional circuitcomponents that can be used in the mobile wireless communications deviceof FIGS. 1-2.

FIG. 4 is front elevational view of the mobile wireless communicationsdevice having the front cover removed to illustrate an example of RFcircuitry, power amplifier, surface mounted microphone and noiseisolation components associated thereof.

FIG. 5 is a fragmentary, isometric drawing of a prior art RF metalshield covering an RF transceiver on a printed circuit board.

FIG. 6 is a fragmentary, isometric drawing of an RF metal shield thatincludes an RF absorber formed as absorbing material positioned at anopening of the RF metal shield to aid in reducing RF energy radiatedfrom an RF component such as part of an RF transceiver chip set into theRF metal shield and causing electromagnetic coupling or electromagneticinterference with other portions of the RF components or chip set withinthe RF metal shield.

FIG. 7 is a fragmentary side elevation drawing of the RF metal shieldand RF absorbing material positioned at an opening within the RF metalshield and covering a portion of an RF transceiver multi-chip module.

FIG. 8 is another embodiment showing the RF metal shield and the RFabsorber formed as a long and narrow slot on the RF metal shield toreduce RF coupling.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Different embodiments will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsare shown. Many different forms can be set forth and describedembodiments should not be construed as limited to the embodiments setforth herein. Rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope to those skilled in the art. Like numbers refer to like elementsthroughout.

A mobile wireless communications device includes a housing and circuitboard carried by the housing and having RF circuitry comprising at leastone RE component, and a plurality of other components mounted on thecircuit board. An RF metal shield is secured to the circuit board andsurrounds and isolates the at least one RF component and plurality ofother components within the RF metal shield. An RF absorber ispositioned adjacent an area of the RF component that radiates energy toaid in reducing any energy radiated from the RF component into the RFmetal shield. As a result, the electromagnetic coupling or interferencewith other portions of the RF component or other components within theRF metal shield is reduced.

The RF shield, in one non-limiting example, has an opening at an area ofthe RF component that radiates energy. The RF absorber is formed as anRF absorbing material positioned at the opening of the RF metal shield.This RF absorbing material could be formed as a ferrite material, andpreferably as a planar sheet that could be secured by adhesive tape tothe RF metal shield. The RF absorber could also be formed as alongitudinal slot positioned over the area of the RF component thatradiates RF energy.

In another non-limiting example, the RF component can be formed as an RFchip set and preferably as a transceiver chip set that could be formedas a transmitter chip, receiver chip and local oscillator chip. The RFabsorber can be positioned adjacent the transmitter chip. The REFcircuitry could also be operative for generating Global System forMobile (GSM) communications packet bursts. The RF circuitry could alsoinclude an RF transceiver, multi-chip module and associated RFcomponents.

A method aspect is also set forth.

A brief description will now proceed relative to FIGS. 1-3, whichdisclose an example of a mobile wireless communications device, forexample, a handheld portable cellular radio, which can incorporate thenon-limiting examples of the various circuits. FIGS. 1-3 arerepresentative non-limiting examples of the many different types offunctional circuit components and their interconnection.

Referring initially to FIGS. 1 and 2, an example of a mobile wirelesscommunications device 20, such as a handheld portable cellular radio isfirst described. This device 20 illustratively includes a housing 21having an upper portion 46 and a lower portion 47, and a dielectricsubstrate (i.e., circuit board) 67, such as a conventional printedcircuit board (PCB) substrate, for example, carried by the housing. Ahousing cover (not shown in detail) would typically cover the frontportion of the housing. The term circuit board 67 as used hereinaftercan refer to any dielectric substrate, PCB, ceramic substrate or othercircuit carrying structure for carrying signal circuits and electroniccomponents within the mobile wireless communications device 20. Theillustrated housing 21 is a static housing, for example, as opposed to aflip or sliding housing which are used in many cellular telephones.However, these and other housing configurations may also be used.

Circuitry 48 is carried by the circuit board 67, such as amicroprocessor, memory, one or more wireless transceivers (e.g.,cellular, WLAN, etc.), which includes RF circuitry, including audio andpower circuitry, including any keyboard circuitry. It should beunderstood that keyboard circuitry could be on a separate keyboard,etc., as will be appreciated by those skilled in the art. A battery (notshown) is also preferably carried by the housing 21 for supplying powerto the circuitry 48. The term RF circuitry could encompass theinteroperable RF transceiver circuitry, power circuitry and audiocircuitry.

Furthermore, an audio output transducer 49 (e.g., a speaker) is carriedby an upper portion 46 of the housing 21 and connected to the circuitry48. One or more user input interface devices, such as a keypad(keyboard) 23 (FIG. 2), is also preferably carried by the housing 21 andconnected to the circuitry 48. The term keypad as used herein alsorefers to the term keyboard, indicating the user input devices havinglettered and/or numbered keys commonly known and other embodiments,including multi-top or predictive entry modes. Other examples of userinput interface devices include a scroll wheel 37 and a back button 36.Of course, it will be appreciated that other user input interfacedevices (e.g., a stylus or touch screen interface) may be used in otherembodiments.

An antenna 45 is preferably positioned at the lower portion 47 in thehousing and can be formed as a pattern of conductive traces that make anantenna circuit, which physically forms the antenna. It is connected tothe circuitry 48 on the main circuit board 67. In one non-limitingexample, the antenna could be formed on an antenna circuit board sectionthat extends from the circuit board at the lower portion of the housing.By placing the antenna 45 adjacent the lower portion 47 of the housing21, the distance is advantageously increased between the antenna and theuser's head when the phone is in use to aid in complying with applicableSAR requirements. Also, a separate keyboard circuit board could be used.

More particularly, a user will typically hold the upper portion of thehousing 21 very close to his head so that the audio output transducer 49is directly next to his ear. Yet, the lower portion 47 of the housing 21where an audio input transducer (i.e., microphone) is located need notbe placed directly next to a user's mouth, and can be held away from theuser's mouth. That is, holding the audio input transducer close to theuser's mouth may not only be uncomfortable for the user, but it may alsodistort the user's voice in some circumstances. In addition, theplacement of the antenna 45 adjacent the lower portion 47 of the housing21 also advantageously spaces the antenna farther away from the user'sbrain.

Another important benefit of placing the antenna 45 adjacent the lowerportion 47 of the housing 21 is that this may allow for less impact onantenna performance due to blockage by a user's hand. That is, userstypically hold cellular phones toward the middle to upper portion of thephone housing, and are therefore more likely to put their hands oversuch an antenna than they are an antenna mounted adjacent the lowerportion 47 of the housing 21. Accordingly, more reliable performance maybe achieved from placing the antenna 45 adjacent the lower portion 47 ofthe housing 21.

Still another benefit of this configuration is that it provides moreroom for one or more auxiliary input/output (I/O) devices 50 to becarried at the upper portion 46 of the housing. Furthermore, byseparating the antenna 45 from the auxiliary I/O device(s) 50, this mayallow for reduced interference therebetween.

Some examples of auxiliary I/O devices 50 include a WLAN (e.g.,Bluetooth, IEEE 802.11) antenna for providing WLAN communicationcapabilities, and/or a satellite positioning system (e.g., GPS, Galileo,etc.) antenna for providing position location capabilities, as will beappreciated by those skilled in the art. Other examples of auxiliary I/Odevices 50 include a second audio output transducer (e.g., a speaker forspeaker phone operation), and a camera lens for providing digital cameracapabilities, an electrical device connector (e.g., USB, headphone,secure digital (SD) or memory card, etc.).

It should be noted that the term “input/output” as used herein for theauxiliary I/O device(s) 50 means that such devices may have input and/oroutput capabilities, and they need not provide both in all embodiments.That is, devices such as camera lenses may only receive an opticalinput, for example, while a headphone jack may only provide an audiooutput.

The device 20 further illustratively includes a display 22, for example,a liquid crystal display (LCD) carried by the housing 21 and connectedto the circuitry 48. A back button 36 and scroll wheel 37 can also beconnected to the circuitry 48 for allowing a user to navigate menus,text, etc., as will be appreciated by those skilled in the art. Thescroll wheel 37 may also be referred to as a “thumb wheel” or a “trackwheel” in some instances. The keypad 23 illustratively includes aplurality of multi-symbol keys 24 each having indicia of a plurality ofrespective symbols thereon. The keypad 23 also illustratively includesan alternate function key 25, a next key 26, a space key 27, a shift key28, a return (or enter) key 29, and a backspace/delete key 30.

The next key 26 is also used to enter a “*” symbol upon first pressingor actuating the alternate function key 25. Similarly, the space key 27,shift key 28 and backspace key 30 are used to enter a “0” and “#”,respectively, upon first actuating the alternate function key 25. Thekeypad 23 further illustratively includes a send key 31, an end key 32,and a convenience (i.e., menu) key 39 for use in placing cellulartelephone calls, as will be appreciated by those skilled in the art.

Moreover, the symbols on each key 24 are arranged in top and bottomrows. The symbols in the bottom rows are entered when a user presses akey 24 without first pressing the alternate function key 25, while thetop row symbols are entered by first pressing the alternate functionkey. As seen in FIG. 2, the multi-symbol keys 24 are arranged in thefirst three rows on the keypad 23 below the send and end keys 31, 32.Furthermore, the letter symbols on each of the keys 24 are arranged todefine a QWERTY layout. That is, the letters on the keypad 23 arepresented in a three-row format, with the letters of each row being inthe same order and relative position as in a standard QWERTY keypad.

Each row of keys (including the fourth row of function keys 25-29) isarranged in five columns. The multi-symbol keys 24 in the second, third,and fourth columns of the first, second, and third rows have numericindicia thereon (i.e., 1 through 9) accessible by first actuating thealternate function key 25. Coupled with the next, space, and shift keys26, 27, 28, which respectively enter a “*”, “0”, and “#” upon firstactuating the alternate function key 25, as noted above, this set ofkeys defines a standard telephone keypad layout, as would be found on atraditional touch-tone telephone, as will be appreciated by thoseskilled in the art.

Accordingly, the mobile wireless communications device 20 as describedmay advantageously be used not only as a traditional cellular phone, butit may also be conveniently used for sending and/or receiving data overa cellular or other network, such as Internet and email data, forexample. Of course, other keypad configurations may also be used inother embodiments. Multi-tap or predictive entry modes may be used fortyping e-mails, etc. as will be appreciated by those skilled in the art.

The antenna 45 is preferably formed as a multi-frequency band antenna,which provides enhanced transmission and reception characteristics overmultiple operating frequencies. More particularly, the antenna 45 isdesigned to provide high gain, desired impedance matching, and meetapplicable SAR requirements over a relatively wide bandwidth andmultiple cellular frequency bands. By way of example, the antenna 45preferably operates over five bands, namely a 850 MHz Global System forMobile Communications (GSM) band, a 900 MHz GSM band, a DCS band, a PCSband, and a WCDMA band (i.e., up to about 2100 MHz), although it may beused for other bands/frequencies as well. To conserve space, the antenna45 may advantageously be implemented in three dimensions although it maybe implemented in two-dimensional or planar embodiments as well.

The mobile wireless communications device shown in FIGS. 1 and 2 canincorporate e-mail and messaging accounts and provide differentfunctions such as composing e-mail, PIN messages, and SMS messages. Thedevice can manage messages through an appropriate menu that can beretrieved by choosing a messages icon. An address book function couldadd contacts, allow management of an address book, set address bookoptions and manage SIM card phone books. A phone menu could allow forthe making and answering of phone calls using different phone features,managing phone call logs, setting phone options, and viewing phoneinformation. A browser application could permit the browsing of webpages, configuring a browser, adding bookmarks, and changing browseroptions. Other applications could include a task, memo pad, calculator,alarm and games, as well as handheld options with various references.

A calendar icon can be chosen for entering a calendar program that canbe used for establishing and managing events such as meetings orappointments. The calendar program could be any type of messaging orappointment/meeting program that allows an organizer to establish anevent, for example, an appointment or meeting.

A non-limiting example of various functional components that can be usedin the exemplary mobile wireless communications device 20 of FIGS. 1 and2 is further described in the example below with reference to FIG. 3.The device 20 illustratively includes a housing 120, a keypad 140 and anoutput device 160. The output device 160 shown is preferably a display,which is preferably a full graphic LCD. Other types of output devicesmay alternatively be used. A processing device 180 is contained withinthe housing 120 and is coupled between the keypad 140 and the display160. The processing device 180 controls the operation of the display160, as well as the overall operation of the mobile device 20, inresponse to actuation of keys on the keypad 140 by the user.

The housing 120 may be elongated vertically, or may take on other sizesand shapes (including clamshell housing structures). The keypad mayinclude a mode selection key, or other hardware or software forswitching between text entry and telephony entry.

In addition to the processing device 180, other parts of the mobiledevice 20 are shown schematically in FIG. 3. These include acommunications subsystem 101; a short-range communications subsystem102; the keypad 140 and the display 160, along with other input/outputdevices 106, 108, 110 and 112; as well as memory devices 116, 118 andvarious other device subsystems 121. The mobile device 20 is preferablya two-way RF communications device having voice and data communicationscapabilities. In addition, the mobile device 20 preferably has thecapability to communicate with other computer systems via the Internet.

Operating system software executed by the processing device 180 ispreferably stored in a persistent store, such as the flash memory 116,but may be stored in other types of memory devices, such as a read onlymemory (ROM) or similar storage element. In addition, system software,specific device applications, or parts thereof, may be temporarilyloaded into a volatile store, such as the random access memory (RAM)118. Communications signals received by the mobile device may also bestored in the RAM 118.

The processing device 180, in addition to its operating systemfunctions, enables execution of software applications 130A-130N on thedevice 20. A predetermined set of applications that control basic deviceoperations, such as data and voice communications 130A and 130B, may beinstalled on the device 20 during manufacture. In addition, a personalinformation manager (PIM) application may be installed duringmanufacture. The PIM is preferably capable of organizing and managingdata items, such as e-mail, calendar events, voice mails, appointments,and task items. The PIM application is also preferably capable ofsending and receiving data items via a wireless network 141. Preferably,the PIM data items are seamlessly integrated, synchronized and updatedvia the wireless network 141 with the device user's corresponding dataitems stored or associated with a host computer system.

Communication functions, including data and voice communications, areperformed through the communications subsystem 101, and possibly throughthe short-range communications subsystem. The communications subsystem101 includes a receiver 150, a transmitter 152, and one or more antennae154 and 156. In addition, the communications subsystem 101 also includesa processing module, such as a digital signal processor (DSP) 158, andlocal oscillators (LOs) 161. The specific design and implementation ofthe communications subsystem 101 is dependent upon the communicationsnetwork in which the mobile device 20 is intended to operate. Forexample, the mobile device 20 may include a communications subsystem 101designed to operate with the Mobitex™, Data TAC™ or General Packet RadioService (GPRS) mobile data communications networks, and also designed tooperate with any of a variety of voice communications networks, such asAMPS, TDMA, CDMA, PCS, GSM, etc. Other types of data and voice networks,both separate and integrated, may also be utilized with the mobiledevice 20.

Network access requirements vary depending upon the type ofcommunication system. For example, in the Mobitex and DataTAC networks,mobile devices are registered on the network using a unique personalidentification number or PIN associated with each device. In GPRSnetworks, however, network access is associated with a subscriber oruser of a device. A GPRS device therefore requires a subscriber identitymodule, commonly referred to as a SIM card, in order to operate on aGPRS network.

When required network registration or activation procedures have beencompleted, the mobile device 20 may send and receive communicationssignals over the communication network 141. Signals received from thecommunications network 141 by the antenna 154 are routed to the receiver150, which provides for signal amplification, frequency down conversion,filtering, channel selection, etc., and may also provide analog todigital conversion. Analog-to-digital conversion of the received signalallows the DSP 158 to perform more complex communications functions,such as demodulation and decoding. In a similar manner, signals to betransmitted to the network 141 are processed (e.g., modulated andencoded) by the DSP 158 and are then provided to the transmitter 152 fordigital to analog conversion, frequency up conversion, filtering,amplification and transmission to the communication network 141 (ornetworks) via the antenna 156.

In addition to processing communications signals, the DSP 158 providesfor control of the receiver 150 and the transmitter 152. For example,gains applied to communications signals in the receiver 150 andtransmitter 152 may be adaptively controlled through automatic gaincontrol algorithms implemented in the DSP 158.

In a data communications mode, a received signal, such as a text messageor web page download, is processed by the communications subsystem 101and is input to the processing device 180. The received signal is thenfurther processed by the processing device 180 for an output to thedisplay 160, or alternatively to some other auxiliary I/O device 106. Adevice user may also compose data items, such as e-mail messages, usingthe keypad 140 and/or some other auxiliary I/O device 106, such as atouchpad, a rocker switch, a thumb-wheel, or some other type of inputdevice. The composed data items may then be transmitted over thecommunications network 141 via the communications subsystem 101.

In a voice communications mode, overall operation of the device issubstantially similar to the data communications mode, except thatreceived signals are output to a speaker 110, and signals fortransmission are generated by a microphone 112. Alternative voice oraudio I/O subsystems, such as a voice message recording subsystem, mayalso be implemented on the device 20. In addition, the display 160 mayalso be utilized in voice communications mode, for example to displaythe identity of a calling party, the duration of a voice call, or othervoice call related information.

Any short-range communications subsystem enables communication betweenthe mobile device 20 and other proximate systems or devices, which neednot necessarily be similar devices. For example, the short-rangecommunications subsystem may include an infrared device and associatedcircuits and components, or a Bluetooth™ communications module toprovide for communication with similarly-enabled systems and devices.

FIG. 4 is an example of a circuit layout on part of the circuit board 67that can be included within the mobile wireless communications device 20of FIGS. 1-3, and showing a front cover removed from a housing toillustrate a surface mounted microphone 200 and its circuitry andassociated noise isolation components as will be explained in greaterdetail below. The circuit board 67 includes radio frequency (RF)circuitry, for example, cellular telephone communications circuitry,which is mounted in first and second isolation RF metal shields or“cans” 210,212, as often called by those skilled in the art, forming acompartment on the circuit board, each which receive the RF circuitryand other components, which typically are RF components. Each can210,212 forms a radio frequency isolation compartment and typicallyincludes sides and a top, such as a portion of the top 210 a shownremaining on can 210. The first can 210 includes a transceiver chip set220, for example, a transmitter chip, receiver chip, and localoscillator chip as non-limiting examples with those chips labeled A, Band C. The chip set could, in non-limiting examples, be formed as an RFtransceiver multi-chip module. Other illustrated components couldinclude the various resistors, capacitors, amplifiers, regulators andother circuit components common to those devices, but not explained indetail.

Located outside first and second isolation cans 210,212, but mounted onthe circuit board 67, is a liquid crystal display (LCD) connector 230and a keyboard connector 232, as well as associated circuit components234. These components 230, 232 and 234 can be configured in differentconfigurations besides the configuration illustrated in the non-limitingexample of FIG. 4. The compartment within the second isolation can 212includes a power amplifier 236 and switch diplexer 238. Other components240 are mounted within the compartment and form the resistors,capacitors, transistors, and inductors necessary to drive the audio andpower circuits for the microphone, power amplifier and other circuits.

To provide microphone isolation, a radio frequency isolation shield 250,formed in the illustrated non-limiting example as a third isolation“can” 250, is positioned at a corner of the second “can” 212, and formsanother isolation compartment at this corner. The shield is formed as aseparate metallic housing secured to the circuit board and surroundingthe microphone, effectively covering, i.e., shielding the entiremicrophone. Although a “can” configuration formed as a metallic housingwith top and sides and is used for the RF shield, other configurationscould be used. The compartment formed by the isolation shield 250receives a microphone 200 formed preferably as a surface mountedmicrophone integrated circuit chip 200 on the circuit board 67. Asillustrated in this non-limiting configuration, this places themicrophone chip adjacent to the bottom center of the device 20 where thesound hole is typically located in the cover of a cellular phone orsimilar mobile wireless communications device.

To reduce noise resulting from RF circuitry, the metal RF shield or“can” forming an isolation shield includes a side and top metal wall,i.e., forming a complete isolation shield surrounding or covering themicrophone 200 and its associated circuitry to provide isolation fromthe RF circuitry. This isolation shield provides the necessary isolationfrom the RF amplifiers and from any energy radiated from the antenna.

Referring now to FIG. 5, a circuit board 300, such as the type explainedrelative to FIGS. 1-4, is shown and includes an RF transceiver 302mounted thereon, which could correspond to an RE transceiver multi-chipmodule as explained before, and having transmitter, receiver and localoscillator chips as explained before. The RF transceiver 302 is coveredby an RF metal shield 304 as explained before. In this prior artexample, the entire RF transceiver 302 is covered by the REF metalshield. In some instances, the RE energy from one portion of the RFtransceiver or other RF component is generated into the RF metal shieldand cause electromagnetic coupling or interference with certain sectionsof the RF transceiver or other RE components within the RF metal shield.

In accordance with one non-limiting example, the RF metal shield 308shown in FIG. 6 has been modified to include an opening 310 positionedat that area or section of the RF transceiver or other RF component thatradiates RF energy. An RF absorber 312 is formed as an RF absorbingmaterial in this illustrated embodiment and positioned at the opening,i.e., adjacent that area of the RF component, such as the transceiver orchip that radiates RF energy, to aid in reducing RF energy radiated fromthe component into the RE metal shield and causing electromagneticcoupling or interference with other portions of the RE component or chipwithin the RE metal shield. This RF absorbing material 312 in theillustrated embodiment is formed as a ferrite material, preferablyformed and as a planar sheet. Adhesive tape 314 can secure the RFabsorbing material 312 to the RF metal shield. Of course, the RFtransceiver is shown as one unit, such as an RF transceiver/multi-chipmodule, but it could include the basic transmitter chip, receiver chipand local oscillator chips labeled A, B and C as shown in FIG. 7, whichare shown positioned in a multi-chip module and adjacent other RF andperhaps non-RE components 320 that are within the confines of the RFmetal shield.

The RF absorbing material can be formed of different ferrite materialsand typically has an applicable frequency of about 0.1 to about 3.0 GHz.An example of such RF absorbing material is the microwave absorbingmaterial sold under the designation EA20/EA21 by Murata ManufacturingCompany, Ltd. The thickness in non-limiting examples can range fromabout 0.05 millimeters to about 3.00 millimeters. The structure can behalogen free and have a flame resistance and operating temperature rangefrom about −40 to about +120° C. Adhesive tape can be used to secure thematerial to an object, for example, the RE metal shield in this example.The material can be formed from an Ni—Zn ferrite material in onenon-limiting example, and can have a specific gravity of about 3.4 (Typ)and a tensile strength of 3.0 MPa (min) and a surface resistance ofabout 1.0×10¹¹ (min), in non-limiting examples. Flame resistance can becompatible to UL940V-O.

FIG. 8 shows another RF metal shield 330 in which the RE absorber isformed as a longitudinally extending, but narrow slot 332 that is on themetal shield and positioned over that portion of the RE component thatemits the RF radiation to prevent RF coupling as described before. Inthis specific instance, the longitudinal slot is operable to break-upthe RF energy from coupling into the metal shield and onto othercomponents, thus reducing the undesirable electromagnetic interferenceand electromagnetic coupling.

Many modifications and other embodiments of the invention will come tothe mind of one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is understood that the invention is not to be limited tothe specific embodiments disclosed, and that modifications andembodiments are intended to be included within the scope of the appendedclaims.

1. A mobile wireless communications device, comprising: a housing; acircuit board carried by the housing and having RF circuitry comprisingat least one RF component and plurality of other components mounted onsaid circuit board; an RF metal shield secured to said circuit board andsurrounding and isolating said at least one RF component and pluralityof other components within said RF metal shield, said RF metal shieldhaving an RF absorber positioned adjacent an area of the RF componentthat radiates energy to aid in reducing energy radiated from the RFcomponent into the RF metal shield and causing electromagnetic couplingor interference with other portions of said RF component or othercomponents within said RF metal shield, wherein said RF metal shield hasan opening at an area of the RF component that radiates energy and saidRF absorber comprises an RF absorbing material positioned at the openingof the RF metal shield.
 2. A mobile wireless communications deviceaccording to claim 1, wherein said RF absorbing material comprises aferrite material.
 3. A mobile wireless communications device accordingto claim 2, wherein said RF absorbing material comprises a planar sheet.4. A mobile wireless communications device according to claim 3, andfurther comprising an adhesive tape securing to said RF metal shieldsaid planar sheet that forms said RF absorbing material.
 5. A mobilewireless communications device according to claim 1, wherein said RFabsorber is formed as a longitudinal slot positioned over the area ofthe RF component that radiates energy.
 6. A mobile wirelesscommunications device according to claim 1, wherein said at least one RFcomponent comprises an RF chip set.
 7. A mobile wireless communicationsdevice according to claim 6, wherein said RF chip set comprises atransceiver chip set.
 8. A mobile wireless communications deviceaccording to claim 7, wherein said chip set comprises a transmitterchip, receiver chip and local oscillator chip.
 9. A mobile wirelesscommunications device according to claim 8, wherein said RF absorber ispositioned adjacent said transmitter chip.
 10. A mobile wirelesscommunications device according to claim 1, wherein said RF circuitry isoperative for generating Global System for Mobile (GSM) communicationspacket bursts.
 11. A mobile wireless communications device, comprising:a housing; a circuit board carried by the housing and having a RFcircuitry comprising a plurality of RF components including an RFtransceiver multi-chip module mounted on said circuit board; a RF metalshield secured to said circuit board and surrounding and isolating saidRF components and RF transceiver multi-chip module within said RF metalshield, said RF metal shield comprising a planar top surface and havingan opening at the top surface in a position where said RF transceivermulti-chip module radiates energy, and an RF absorbing materialpositioned at the opening to aid in reducing radiation emitted from theRF transceiver multi-chip module into the RF metal shield and causingelectromagnetic coupling or interference with other portions of said RFtransceiver multi-chip module or other RF components enclosed by said RFmetal shield.
 12. A mobile wireless communications device according toclaim 11, wherein said RF absorbing material comprises a ferritematerial.
 13. A mobile wireless communications device according to claim12, wherein said RF absorbing material comprises a planar sheet.
 14. Amobile wireless communications device according to claim 13, and furthercomprising an adhesive tape securing said planar sheet forming said RFabsorbing material to said RF metal shield.
 15. A mobile wirelesscommunications device according to claim 11, wherein said RF circuitryis operative for generating Global System for Mobile (GSM)communications packet bursts.
 16. A method for making a mobile wirelesscommunications device, which comprises: providing a housing, a circuitboard carried by the housing, radio frequency (RF) circuitry includingat least one RF component and other components carried by the circuitboard, and a RF metal shield secured to said circuit board andsurrounding and isolating said at least one RF component and othercomponents within said RF metal shield; reducing energy radiated from aportion of an RF component into the RF metal shield to reduce theelectromagnetic coupling or interference with other portions of said RFcomponent or other components enclosed by said RF metal shield bypositioning an RF absorber adjacent the area of the RF component thatradiates energy; and forming a slot within the RF metal shield over theportion of the at least one RF component that radiates energy.
 17. Amethod according to claim 16, which further comprises forming the atleast one RF component as an RF chip set.
 18. A method according toclaim 16, which further comprises forming an opening in the RF metalshield and positioning an RF absorbing material at the opening to formthe RF absorber.
 19. A method according to claim 18, which furthercomprises forming the RF absorbing material as a ferrite material.
 20. Amobile wireless communications device, comprising: a housing; a circuitboard carried by the housing and having RF circuitry comprising at leastone RF component and plurality of other components mounted on saidcircuit board; an RF metal shield secured to said circuit board andsurrounding and isolating said at least one RF component and pluralityof other components within said RF metal shield, said RF metal shieldhaving an RF absorber positioned adjacent an area of the RF componentthat radiates energy to aid in reducing energy radiated from the RFcomponent into the RF metal shield and causing electromagnetic couplingor interference with other portions of said RF component or othercomponents within said RF metal shield, wherein said RF absorber isformed as a longitudinal slot positioned over the area of the RFcomponent that radiates energy.
 21. A method for making a mobilewireless communications device, which comprises: providing a housing, acircuit board carried by the housing, radio frequency (RF) circuitryincluding at least one RF component and other components carried by thecircuit board, and a RF metal shield secured to said circuit board andsurrounding and isolating said at least one RF component and othercomponents within said RF metal shield; reducing energy radiated from aportion of an RF component into the RF metal shield to reduce theelectromagnetic coupling or interference with other portions of said RFcomponent or other components enclosed by said RF metal shield bypositioning an RF absorber adjacent the area of the RF component thatradiates energy; and forming an opening in the RF metal shield andpositioning an RF absorbing material at the opening to form the RFabsorber.